What is a VIP tour?

VIP private tours are becoming popular with tourists in many places. These tours are back stage, all access passes so to speak, where you can experience things other guests can not. You get to see things others don’t, and get special treatment. These are purchased separately or can be given by the owner or manager by choice or at random.
How much can something like this cost?
A tour like this can cost anywhere from $300+ and get into the thousands.